Electric computer



Marph 25, 1958 D. M. BOYD, JR 25828070 ELECTRIC COMPUTER I Filed Dec.s1, 1954 David M Boyd Jr.

A TTOR/VEYS.'

ELECTRIC COMPUTER David M. Boyd, Sir., Clarendon Hills, Ill., assignerto Universal @il Products Company, Des Plaines, lll., a corporation ofDelaware Application December 31, 1954, Serial No. 47 8,97 1

2 Claims. (Cl. 23S- 61) This invention relates to an electric computerfor simultaneously solving inter-related equations and in particular toan electric computer especially adapted to making tray by traytemperature and composition calculations for designing fractionation orother multi-stage equipment.

`Many problems in engineering and research require the solution of long,complex series of inter-related mathematical equations in order toarrive at a proper design for equipment or to determine the course of areaction. Frequently, in the solution of these equations each stage ofsolution depends upon the solution of the last previous stage so that anultimate answer to the problem is dificult to obtain in a short periodof time since the various parts of the problem cannot be worked onindependently by several people. Typical of these problems are thoseassociated with the design of rnulti-stage equipment such asfractionation columns, multiple effect evaporators, liquid-liquid orliquid-solid extraction processes, etc. The design of the equipment forthese processes requires long hours of routine work which must beaccomplished by highly trained men who could be better used for morecreative problems. he laborious manual solution of complex mathematicalequations also invites human error which frequently requiresrecalculations to be made or alternatively incorporates mistakes intothe ultimate design. lt is an object of this invention to rapidly andaccurately calculate such problems by electric means.

To accomplish this object it is an embodiment of this invention toprovide an electric computer comprising in combination a constantvoltage source connected to a plurality of identical parallel circuits,each of said circuits comprising a first voltage dividing meansconnected to a bank of parallel first voltage multiplying means whichare adapted to be preset to speciiic multipliers, suitable programingmeans for alternately inserting pairs of consecutive lirst multiplyingmeans into an interpolating bal-I ancing circuit which adds the voltagesto similarly obtained voltages from the other parallel circuits andbalances the circuit at said constant voltage when one of the sums ofthe consecutive pairs of iirst multiplying means causes one voltagegreater and one voltage less than said constant voltage, recording meansto record the position of balance of said interpolating circuit as theproportion` of the dilference that said constant voltage is from saidgreater voltage and said less voltage, second multiplying means adaptedto be preset to specific multipliers connected one to a fixed voltagedividingmeans to multiply the iixed divided voltage and another tomultiply the voltage obtained by one of the pair of the aforesaid lirstmultiplying means, a second adding circuit connected to said secondmultiplying means whereby their voltages are added, balancing meansconnected to said second adding circuit and to a second voltage dividingmeans whereby the resultant sum of the voltages is balanced against saidconstant voltage to obtain a voltage equal to said sum from said secondvoltage dividing means, connecting said tates Patent" y second voltagedividing means to a bank of parallel riice fourth multiplying meanswhich are adapted to be preset to specific multipliers, suitableprograming means for alternately inserting consecutive pairs of fourthmultiplying means into a second interpolating balancing circuit whichadds the voltages to similarly obtained voltages from the other parallelcircuits and balances the circuit at said constant voltage when one ofthe sums of the consecutive pairs of fourth multiplying means causes onevoltage greater and one voltage less than said constant voltage,connecting said second interpolating circuit to said recording means torecord the position of balance of said interpolating circuit as aproportion of the difference that said constant voltage is from saidgreater and said less voltage, fifth multiplying means adapted to bepreset to specific multipliers connected one to said xed voltagedividing means to multiply the resultant fixed voltage and another tomultiply the voltage obtained from one of the pairs of the aforesaidfourth multiplying means, a fourth adding circuit connected to saidfifth multiplying means whereby the voltages are added, balancing meansconnected to said fourth adding circuit and to said rst voltage dividingmeans whereby the sum of the voltages is balanced against said constantvoltage to obtain a voltage from said first voltage dividing means equalto said sum from said voltage dividing means.

Since the apparatus and method of this equation are particularly adaptedto aiding in the design of fractionation columns it Will be described inrelation thereto, however, it is to be understood that this choice of anexample is not intended to be limiting on the apparatus or its function.of a series of identical parallel circuits for each component of amixture to be fractionated. Therefore, a two component system will havetwo parallel circuits and a live component system will `have liveParallel circuits,

however, some systems contain hundreds of components,`

for example, a petroleum fraction, and in these cases a circuit will beused for each boiling range desired instead of each component. Each ofthe parallel circuits representing a component or a boiling range iscomprised of a voltage dividing means for establishing a voltageproportional to the desired purityof that component and a series ofparallel voltage multiplying means which are programmed to function asconsecutive pairs until a proper pair is in the circuit. That ismultiplying means 1 and 2 Will function as a pair and then multiplyingmeans 2 and 3 will function as a pair, next 3 and 4, etc. There may beas many multiplying means in each of these banks as desired, the numberbeing chosen in accordance with the accuracy desired.

Each parallel circuit also contains asecond group of multiplying meansfor correcting' an answer obtained in the first group for the influenceof another stream.

Since the operation of this apparatus is rather conn plex it may be bestdescribed with reference to the ac,

companying drawing which illustrates an extremely simpley embodiment andis not to be limiting on this invention.

rEhe drawimy illustrates a circuit established to desifin 4,

fractionator for a two component system that is desired to produce apure overhead from the mixture ot`v 'l` his column are condensed andreturned to the top tray and one part is withdrawn as product. In theexplanation, K is the constant (at a specic temperature and pressure)from equation Y=KX where Y is the mol percent of one component'in1 the.l vapor phase and X is the mol percent of that componentr Basically theapparatus of this invention consists in the liquid phase' from which thevapor came, or the liquid phase in equilibrium with that vapor. El isany base voltage and for the purposes of this explanation it will beconsidered 100 volts,V however, itis understood thatl any voltage may besuitable. imposed across the circuit by connecting` voltage` dividingmeans 1, 2, 3 and 4 to a suitable source of power and to the ground.Voltage dividing means l. and 3 are setto take a percent of the basevoltage equivalent to the desired percent of light component in theproduct from the column. Therefore, in this example, since it is desiredto have 95% purity of light material in the product, voltage dividingmeans 1 and 3 will be set to take 95% of the base voltage or in thiscase 95 volts. Thus, in lines 5 and 21 a potential of 95 volts exists.The function of line 21 will be considered later and will not bediscussed further at this point.

Similarly, voltage dividing means 2 and 4 are set to establish a voltageproportional to the percent of heavy material in the overhead productand in this case, since theY percent of light material and heavymaterial must be 100, voltage dividing means 2 and 4 are regulated toplace a voltage of 5 volts or 5% of El in lines l2 and 34. As with line21 above described, a detailed discussion of line 34 will be deferred.

It is now desired to obtain the composition ofthe liquid on the top trayof the column from which the vapor containing 95% light material and 5%heavy materiai was obtained. Since K multiplied by the composition ofthe liquid will produce the. answer Y, which is the composition of thevapor, then the composition of the vapor Y multiplied by the reciprocalof K will produce the composition of the liquid in the light materialVfrom which the vapor was obtained. Therefore, voltage multiplying means6 is established in series with line 5 and multiplies the voltage inline 5 by to produce in line 8 avoltage corresponding to the amount oflight material in the liquid phase on the top tray. Similarly, thevoltage in line 5 is transmitted to voltage multiplier 7 wherein it ismultiplied by to produce in line 9 another voltage corresponding to thecomposition in light material of the liquid phase on the top tray.

Since the-true K value is unknown and the K values used are incorrect,the two voltages corresponding to the liquid composition on the top trayareV also not correct, however, this difficulty is overcome by the useof a series of K values and the interpolating circuit. Since it is knownthat the column will operate over a given temperature range and it isalso known that the column will operate over a given composition range,the K value for the components of the mixture to be separated may beknown for a given temperature and composition. Thus, for example, if thecolumn operates over a 100 F. to 200 F. temperature range, K values maybe set into the series of multiplying means corresponding to the K valueof the components at 10 temperature increments over the temperaturerange of operation. The K values are arbitrarily chosen and will usuallyVbe at convenient even increments for example, at each 10. the bank ofmultipliers represents a series of trials at obtaining the value K,which is a number' which quantitatively describes the difference involatility between the two components in the mixture to be separated atthe temperature in the stage being calculated.

Simultaneously with the above described multiplications, the voltage inline 12 which represents the composition Lof the vapor in heaviermaterial is also multiplied by suitable The base voltage is,

In other words, t

Vvalue selecting 4 Kl etc. values by multipliers 13 and 14 respectivelyand whatever additional multipliers are in parallel with these two toestablish in lines 15 and 16 respectively two values for the compositionof the liquid ony the top tray in heavier component. The

the others must also have l0 values. It is also necessary that the evalues in the circuit calculating the light material be diffferent by aproportional amount, which proportional amount represents the ratio ofthe K values of these two components at any temperature. Therefore, ifthe volatility of the light component as compared to the volatility ofthe heavy component were such Vthat. the K value for theV lightcomponent were twice the K value for the heavy component, thecorresponding multipliers in the lparallel circuits would4 differ by aVfactor of 100% in the magnitude, of their eiect upon Vthe input voltageto each of the cor.- respondirigmultipliers. By making the difference inK value proportional between the light material circuit and the heavymaterial circuit one assumes that there is a constant diiererice betweenthe K Values lover the entire temperature range or, in other words, thatthe plot of K versus temperature for the two components would producetwo lines whose distance apart on the graph paper would be substantiallyunchanged over the temperature range involved. Although this assumptionis not strictly true'it is usually made in calculations of fractionatingcolurrms along with assumptions of equal molal boil-up and equal molaloverflow. It has been found from experience that these assumptions aresubstantially true and devia tions fromthem are extremely small andordinarily negligible compared with other quantities involved. YByestablishing Y .l 'values is automatically set. It is of coursenecessary that the mechanisms for the two parallel circuits coact sothatthe same pair of values is in the two circuits at the same time.

The voltages established in lines 8 and 1S, which represent thecomposition of the liquid on the top tray in light material Vand inheavy material are connected to adding circuitl which produces in line17 thesulm of these voltages. VAs hereinbefore stated the amount ofheavy material plus the amount of light material, percentage-wise,should equal or in this case 100 volts. However, since the K values arearbitrarily chosen the sum of the products will probably not be 100volts or E1, but a voltage E3 which will probably be greater than orless than E1. It the value of E3 is equal to the vale of El, then ofcourse the problem of the top tray liquid composition and temperature issolved and the arbitrarily chosen K value is correct, however, if it isnot equal to E1 further calculations must be made and these are made byadding the voltages established in lines 9 and 16, which are equivalentto a second calculation of composition of heavy and light material inthe liquid phase on the top tray. This addition is performed by addingcircuit 11 which produces in line 18 a voltage E3 which will bedifferent from E2.

It is desired that if E2 and E3 are neither equal to E1, one of them ishigher than E1 and one of them is lower than El. When this situationexists E2 and E3 through lines 17 and 18 respectively, are placed atopposite ends of interpolating circuit 19 which establishes the distancebetween them that is proportional to El to obtain the fraction of thedistance between them representing E1 and therefore an interpolationbetween these values for the proper value of K.

lf the arbitrarily chosen values for K are wrong in the same direction,that is if the value Vfor E2 and the value of E3 ultimately arrived atare both higher than or both lower than E1 the circuit will drop themultiplier for out of the circuit, place the multiplier into thatposition in the circuit, that is the voltage obtained by multiplier willbe in line 5, and introduce into the circuit a new value which willconnect to line 6 producing a new voltage therein. Simultaneously, thecircuit calculating the heavier material will drop again be tested bythe interpolating circuit` to see ifone is greater than and one is 4lessthan E1. This operation may be repeated by each succeeding pair ofconsecutive values in the bank until E2 and E3 values bridging E1 areobtained and the interpolation is made to obtain the proper value ofSince these-valueswere established for a specific tem perature, theultimately obtained value for resulting from the interpolation isequivalent to the temperature on the top tray as well as the compositionof the liquid. Suitable recording means connected to the interpolatingmeans, such as a teletype machine adapted to record a particular numberat a specific rest position of a stepping relay, will be connected tothe interpolating means so that the answer ultimately obtained may bepreserved as a permanent record.

The apparatus of this invention hasto this point calculated thetemperature and composition of the liquid on the top tray of the columnand it is now desired to calculate the composition of the vapor comingfrom the second tray down in the column hereinafter called the secondtray or, in other words, the vapor coming to the top tray of the column.

lt is readily seen that the liquid product from the column, or ,1/5 ofthe total boil-up from the top tray of the column must pass through theentire column from the feed point to the top tray in the vapor phase.`As hereinbefore described, assuming equal molal overtlow and equalmolal boil-up on each tray, the top tray has, of its five parts ofoverhead or boil-up, one part lost as product and four parts returningto the tray as reflux.

The reilux, or` its thermal equivalent, goes to the trays below. Itmaybe seen from this description and from the assumption of equal molalboil-up and equal molal overow that the mols of liquid passing to anytray is different from the vapor passing from that tray by the number ofmols of product.

Therefore, the number of mols of liquid passing from the'top tray, thecomposition of this liquid, and the number of mols of vapor coming fromthe second tray are all known. By material balance the composition ofthe vapor can be determined. The composition of the vapor on the secondtray is the sum of the ratio of mols of product to mols of boil-up timesthe product composition plus the ratio of mols of reux to mols ofboil-up times the composition of the liquidfrom the tray above.

To aid in this explanation, a mathematical analysis of the portion ofthe column above` the feed tray may be made. Making V the mols of vaporpassing upwardly through the column, L the mols of liquid passing down,D Vthe mols of product, Y the mol fraction of light material in thevapor and X the mol fraction of light material in the liquid, thefollowing relationships are true:

where subscripts l and 2 indicates the rst and `second trays. Also, bymaterial balance, this equation, as here-v inbefore stated, indicatesthat the mols of vapor diier fromthe mols of liquid by the quantity ofproduct. i

-the top tray, which is equivalent to the product from the column, to Vsof the composition of light material of the liquid phase on the nexthigher tray. It may be seen that if the rellux ratio were l to l thecomposition dierence between the liquid phase on a tray and the vaporphase on the next lower tray would be 1/2 ofthe total boil-up from thetop tray and if the reflux ratio were 3to ,l it would be V4, etc. l v

i liguid passingV to the.` second tray,

7 Y In the operation of thisiin'yention, to'obtain the composition ofthe vapor ontlie second tray, a voltage di- Yiding means 3 is insertedinto Vthe circuit and line 21V carries the voltage taken from thisdividing means toY a multiplying means which multiplies it 'by 1,/5,since theY eQuXratio is 4 to 1, and' transmits this through line 28toad'ding means 30. The voltage dividing means yfor obtaining thisfigure will be set to place a voltage in line 21 proportional tothepurityfof the light material in the product from the column or in thisparticular case 95 'i ill" liquid phase in lilies` 8" and. valu'finay beI p a inthe one of these lines which is closest to the true value.Therefore, double throwsinglepole switch 25V and line 26 areY operatedbyl relay or other means connecting to onthe iirst tray is between theVvoltages 9 and a Vclose approximation to the true the interpolatingcircuit 19 so that eitherline 24 cpzo'nnec't-V ingto line 9` or line 23connecting to line S will be used inthe circuit depending Yupon whichvoltagel is closer toV tha true. value of composition. When one or theother multiplicationV volts. The composition of light materialV made byusing for this value the voltageY isultiinately selected'thevalue ofthat voltagefs trans-Y mittedto voltage multiplier V27 which multipliesit by a factor of valuepreviouslyobtained by multiplyingthe boil-up lonth? top tray by This addition, i lent of adding the amount ofV overhead.product tothe. resiilts ina voltage inY line 31"equivalent to theamounty oflightl material in the vapor'on the second tray.y This voltageis fed into` balancing circuit 32 which mechanically establishes` thesame voltage in line 105 by adjusting the voltage dividing means 1431 toproduce the calfcircuit the composition of "thevapor phase on'the secondtray inheavier material is obtained. from-the sec;

' ond' parallel circuit by means of miltiply'ing the voltage in line l34which is established by placing an initial voltage: of 5 volts frompotentiometer 4 and multiplying the thus obtained voltage by Vsdesir'edfvoltage.Y By an dentiby multiplying means lfand 4/sandtransmits theimultiplied voltage to voltage adding vcircuit wherein itsvalue nis `added to the 25' Whh is the equiva- Y' Y the stripping or.upper portion ofk the the calculations will be stopped and the apparatusreset to calculateffrom thefbottom' tray of they column to the @cdkey-U.Y. Y i VThe 'calculation of thebottom or stripping portion of theAcolumn isaccomplished"by setting, the multiplying means 22 'and 27 forthe light materialcomposition and to .condltlonsin that portion of thecolumn. These calculationsare made according to the equation: Y L1 W1where is the mols of bottoms withdrawn. This equa- Y tion "is derivedsimilarly to the previously used equation rate when-'these` values aredetermined they may readily 'beVv set 4into the apparatus'of thisinvention to calculate the bottom part of the column. Thefvaluecorresponding to Ll/Lf--W being placed in multipliers 27 and 40 andthe'value W/Lf-Wfbeing placed in multipliers 22 and 35'." Whenlthevmultiplying means have been adjusted and the calculations started, theapparatus Yof this invention will calculate eachl tray up from thebottom until the feed tray is reached.

Any suitable known or commercially available parts `may be used in theassembly of the present invention.

The various voltage dividing means that may be used may includepotentiometers of the slide Wire or stepping relay Y type, transformers,electronic circuits, etc. The preferred voltage dividing means arepotentiometers since their accuracy,V simplicity and availability makethen well adapted'to this function and especially the stepping relay Ytype which are easily actuatedfby magnetic means. The

feeding that voltage into adding circuitV 43 through line 41.' Thisvoltage is added to a voltage obtainedby multiplying thevoltage eitherin line 16 or in line 15, whichever is closer to the correct answer,through'ilinc 37 or lavand` selector switch 38 connected to line 39 andmultiplying the thus Vobtained voltage by ,4/5 through multif plyingcircuit 40, adding the` thusl obtained voltage'in adding circuit 43to'poduce la result equivalent to the composition of the vapor on` thesecond tray in heavy material. This voltage isv transmitted by balancingmeans 45 to'voltage dividing means 102 `andrproduces* in line 112lavoltage equivalent` to that composition.

The voltages inlines 165. and,112` represent theA cornf positionf thevapor on theu second tray in light material and in heavy materialrespectively YYand these lines occupy the samepositionin anidenticaljcircuit as arejoccu'pied;

by lines -`5 and 12 in the previously described circuit.- Therefore,attachingL a circuitto linesv 105 and 112 identical to vthose attachedtolines 5A and 12 will produce a calculation that will render thecomposition of the liquid on thel second tray and the4 composition. ofthe vapor on thepthird tray. The second circuitinthe gure is nurnberedso that each partin the circuit corresponds totheA pantin the-MQVionslydescribed circuit having a number l0 0 lass,Y `It, 'may bersevenf thatthe, balancing means 132andsuitable parts which ;"opevrat`eto Vadjustthe voltage in lines 5. and 1.2. so thatv 'Y the circuit used tocalculate thefiirst trayis also used. tof

calsulatetheV thirdl Vtray as. .Well as. the'ffth `trayr,ithe seventhtray, and the` ninth tray; etc. until Vthe feed tray is reachedat whichtime, thccalculations are stopped.

The,secondl setiof circuitsnumbered with the lGO) series Y less in lightmaterial than thejfee'df, as herrebefore'statedV When the compositioniofeither the voltage multiplying meansY and voltage addingrirneansuste'drn'ay be 'commercially'availablefcircuits which arge usuallyV madeup as units to be bodily included into vthe assembly.V These units areusually electronic or electromechanical circuits such as those shown inFigure l. 7(a), (b), V(c) and (d) of Electronic Analog. Computers, byGLA; and r. Kean, erst editi@ publishedV 1952 by McGraw-Hill PublishingCompanyv and since they form lno part of this inventionrexcept fortheirifunction they will not be described in detail herein. The voltagebalancing means may be of any suitable type such as`a null detectorcoupled with a slide wire and serlvoLmoto'r combination or asteppingrelay Acpupled with incremental resistances across each stage."Theprogramming switches may also be steppingy relays or othersequencing switches. Interpolating means employed may' be abalancingmeans installed to perform the particular function of balancing thecircuit toY the lconstant voltage. For example, a slide wire andservomotor :combinationvmayhe used toY balance i y theY circuit betweenB2 and EstoY be equal tothe' voltage El. As hereinbefore stated ltheseVVparts are generally commercially available and it is contemplated thatthe assembly comprising thisV invention will be made of any performthesel functions. Il'clai'm' as my invention:l Y 'i v Y* Y 12- Anelectric computer comprisingin combination a constant voltage sourceconnected toa plurality of iden` tical parallel circuits, each of `said'circuits'comprising a firstivoltage dividing meansgladapted to take aportion of said constantyoltage, connected to a bank of electrij callyparallel irstjvoltage.. multiplying means which are j adaptedto. bepreset',v to specific` multipliers, programing 70V adapted s toVValternately insert pairs of consecutive lirst multiplying meansVV intoan interpolating kcircuit which means connecting to said first voltagemultiplying-rmeans contains addingv means` at opposite sides thereof toadd jue-multiplied @ragga te munipned voltages from the other parallelcircuits and bring the circuit to" rest Yat Y 35 and 0 .for` the heavymaterial composition to conformV said constant voltage when one of thesums of the consecutive pairs of rst multiplying means causes onevoltage greater and one voltage less than said constant voltage,recording means connecting to said interpolating circuit whereby theposition of rest of said interpolating circuit is recorded as thediierence that said constant voltage is from said greater voltage andsaid less voltage, second multiplying means adapted to be preset tospecific multipliers connected one to a fixed voltage dividing means tomultiply the xed divided voltage and another to multiply the voltageobtained by one of the pair of the aforesaid rst multiplying means, asecond adding circuit connected to said second multiplying means wherebytheir voltages are added, balancing means connected to said secondadding circuit and to a second the voltages is balanced against saidconstant voltage to obtain a voltage equal to said sum from said secondvoltage dividing means, means connecting said second voltage dividingmeans to a bank of parallel third multiplying means which are adapted tobe preset to specific multipliers, programing means connected to saidmultiplying means adapted to alternately insert consecutive pairs ofthird multiplying means into a second interpolating circuit whichcontains adding means at opposite ends thereof to add the multipliedvoltages to multiplied voltages from the other parallel circuits andbring the circuit to rest at said constant voltage when one of the sumsof the consecutive pairs of third multiplying means causes voltagedividing means whereby the resultant sum of one voltage greater and onevoltage less than said constant voltage, means connecting said secondinterpolating circuit to said recording means to record the position ofrest `of said interpolating circuit as the difference that said constantvoltage is from said greater and said less voltage, fourth multiplyingmeans adapted to be preset to specific multipliers connected one to saidfixed voltage dividing means to multiply the resultant fixed voltage andanother to multiply the Voltage obtained from one of the pairs of theaforesaid third multiplying means, a fourth adding circuit connected tosaid fourth multiplying means whereby the voltages are added, balancingmeans connected to said fourth adding circuit and to said first voltagedividing means whereby the sum of the voltages is balanced against saidconstant voltage to ootain a voltage from each first voltage dividingmeans equal to said sum from said voltage dividing means.

2. The computer of claim l further characterized in that said banks ofparallel multiplying means in each of said parallel circuits, eachmultiplying means is preset to a value differing from the value of thecorresponding multiplying means in each other parallel circuit by anamount proportional to the difference in volatility of the substances tobe separated.

Bubb May 5, 1953 Bubb June 19, 1955

